Pressure gas release valve for fire suppression

ABSTRACT

A two-step, self-regulating valve ( 16 ) controls gas flow from a gas cylinder ( 12 ) in a high pressure system. The valve ( 16 ) includes a valve body ( 24 ), a piston ( 26 ), a plug ( 28 ), a valve actuator ( 34 ), and a piston actuator ( 32 ). The piston ( 26 ) is movable within the valve body ( 24 ) along an axis between a first and a second position. The plug ( 28 ) is movable within the valve body ( 24 ) along the axis between a valve closed position, a partially open position, and a fully open position. The valve actuator ( 34 ) allows the plug ( 28 ) to move from the valve closed position to the partially open position. The piston actuator ( 32 ) causes the piston ( 26 ) to move from the first position to the second position when a gas pressure in the gas cylinder ( 12 ) is less than a setpoint. When the piston ( 26 ) moves to the second position, the piston ( 26 ) allows the plug ( 28 ) to move from the partially open position to the fully open position.

BACKGROUND OF THE INVENTION

Hazard suppression systems have long been employed for protecting areascontaining valuable equipment or components, such as art galleries, datacenters, and computer rooms. Traditionally, these systems utilize Halon,which is ideal for hazard suppression because it is capable of veryquickly suppressing a hazard, it can be stored at relatively lowpressures, and only a relatively small quantity is required.

However, in recent years the adverse environmental effects of Halon onthe ozone have become evident, and many governmental agencies havebanned further use of Halon. In some countries, existing Halon systemsare being replaced by systems using more environmentally friendly inertgases such as nitrogen, argon, carbon dioxide, and mixtures thereof.Unlike the Halon-based fire suppression systems, inert gas-based systemsuse natural gases and do not contribute to atmospheric ozone depletion.

Combustion occurs when fuel, oxygen, and heat are present in sufficientamounts to support the ignition of flammable material. Inert gas firesuppression systems are based on reducing the level of oxygen in anenclosure to a level that will not sustain combustion. In order toextinguish a fire, inert gas stored in a large number of high-pressurecylinders is released into the enclosure to reduce the concentration ofoxygen by displacing oxygen with the inert gas until combustion isextinguished. Typically, ambient air comprises 21% concentration byvolume of oxygen. This concentration must be reduced to below 14% toeffectively extinguish the fire. To reach this objective, a relativelylarge volume of gas must be released.

There are health and safety implications for facility personnel,particularly in relation to the reduction of oxygen in the atmosphereonce the system is discharged. Careful calculation is required to ensurethat the concentration of inert gas released is sufficient to controlcombustion, yet not so high as to pose a serious risk to personnel.

The replacement of Halon with inert gas for fire protection presents twoissues with the system design. First, the delivery of a large amount of

The replacement of Halon with inert gas for fire protection presents twoissues with the system design. First, the delivery of a large amount ofgas into a protected room within a short period time (fire codes in somecountries require that the gas be delivered in less than one minute) maygenerate overpressure in the room which could potentially damageequipment in the room. Current industrial practice is to use a special,expensive vent in the room to prevent the overpressure. Second, unlikeHalon, inert gas is stored under normal room temperature in gaseousform, rather than liquid form. To reduce the storage vessel volume, avery high pressure is preferred, typically around 100 bar. As a result,the gas distribution system must be capable of withstanding extremelyhigh pressures. These two limitations are key factors in the cost ofboth new installation and retrofit.

The overpressure in the protected room is primarily caused by an unevendischarge of the inert gas from the pressure vessel. The pressure in thegas vessel decays exponentially during gas release, so the overpressuretypically occurs in the first few seconds of the discharge. If the gasrelease can be throttled to a fairly uniform pressure profile over theduration of the discharge, overpressure in the protected room can beprevented while ensuring that the predetermined amount of inert gas isdelivered within the required time.

Throttling the gas flow requires a valve with a controllable variableopening area. While this can be performed by a closed-loop servo valve,high initial and maintaining costs make it an unfavorable approach forfire protection. In addition, the increased system complexity of aclosed-loop control can also introduce reliability concerns.

BRIEF SUMMARY OF THE INVENTION

A two-step, self-regulating valve controls gas flow in a high pressuresystem. The valve includes a valve body, a piston, a plug, a valveactuator, and a piston actuator. The piston is movable within the valvebody along an axis between a first and a second position. The plug ismovable within the valve body along the axis between a valve closedposition, a partially open position, and a fully open position. Thevalve actuator allows the plug to move from the valve closed position tothe partially open position. The piston actuator causes the piston tomove from the first position to the second position when a gas pressurein the gas cylinder is less than a setpoint. When the piston moves tothe second position, the piston allows the plug to move from thepartially open position to the fully open position.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of a fire suppression system inaccordance with the present invention.

FIG. 2 is a perspective view of the fire suppression system inaccordance with the present invention.

FIG. 3 is a partially exploded perspective view of the fire suppressionsystem in accordance with the present invention.

FIG. 4 is a sectional view of the fire suppression system in a fullyclosed position in accordance with the present invention.

FIG. 5 is a sectional view of the fire suppression system in a partiallyopen position in accordance with the present invention.

FIG. 6 is a sectional view of the fire suppression system in a fullyopen position in accordance with the present invention.

FIG. 7 is a sectional view of the fire suppression system in arecharging position in accordance with the present invention.

FIG. 8 is a graph of pressure in an enclosed room to be protected by thefire suppression system in accordance with the present invention as afunction of time.

DETAILED DESCRIPTION

FIG. 1 is a schematic representation of an inert gas-based firesuppression system 10. An plurality of inert gas storage cylinder 12 islocated in a storage area or room proximate an enclosed room 14 to beprotected. Inert gas storage cylinder 12 contains inert gas to bereleased into protected room 14 in case of a fire. Associated withcylinder 12 is a two-step opening high pressure self-regulating valve 16for controllably releasing gas into protected room 14. When a fire isdetected in protected room 14 by a fire detector 18 located in protectedroom 14, a control panel 20 opens self-regulating valve 16. Gas is thendischarged into protected room 14 through discharge nozzles 22 todeplete the concentration of oxygen in protected room 14 and extinguishthe fire.

FIGS. 2 and 3 show a cut-away perspective view and a partially explodedperspective view of regulating valve 16, respectively, and will bediscussed in conjunction with one another. Various portions of FIGS. 2and 3 are shown in light lines to help with the visualization ofself-regulating valve 16. Self-regulating valve 16 generally includesvalve body 24, piston 26, plug 28, hold down spring 30, Bellevillespring 32, and slidable spool 34. Self-regulating valve 16 throttles therelease of inert gas from cylinder 12 in order to control the pressuredischarge into protected room 14.

Valve body 24 has lower section 24A, middle section 24B, and uppersection 24C and generally includes interior cavity 36, gas inlet 44, gasoutlet 46, bleed passage 48, charging port 84, and pressure monitoringport 86. Interior cavity 36 includes plug chamber 38, intermediatesection 40, and piston chamber 42. Plug chamber 38 of interior cavity 36is located in lower section 24A and the lower portion of middle section24B of valve body 24 and has a first diameter D₁ and a second diameterD₂ smaller than first diameter D₁. Piston chamber 42 of interior cavity36 is located in upper section 24C of valve body 24 and has a firstdiameter D₃ and a second diameter D₄ smaller than first diameter D₃.Intermediate section 40 of interior cavity 36 is located in middlesection 24B of valve body 24 between plug and piston chambers 38 and 42and has a diameter D₅ smaller than diameters D₁, D₂, D₃, and D₄ of plugand piston chambers 38 and 42. Piston 26 is housed within lower section24A, middle section 24B, and upper section 24C of valve body 24 and isslidable between a closed position and an open position. Piston 26 inpiston chamber 42 forms control chamber 52 in upper section 24C of valvebody 24. Plug 28 is housed in lower and middle sections 24A and 24B ofvalve body 24 and is slidable between a closed position, a partiallyopen position, and an open position. Plug 28 in plug chamber 38 formsbias chamber 50 in middle section 24B of valve body 24 between plug 28and intermediate section 40 of interior cavity 36. Although valve body24 is depicted in the figures as being formed from a single piece ofmaterial, valve body 24 can be formed from a number of sections that arejoined together by methods known by those skilled in the art.

Bias chamber 50 is located between plug 28 and intermediate section 40of interior cavity 36 and is connected to the atmosphere by bleedpassage 48. Hold down spring 30 is located in bias chamber 50 betweenplug 28 and intermediate section 40 of interior cavity 36 and ispositioned around piston 26. The gas in bias chamber 50 and hold downspring 30 apply pressure to plug 28 and maintain plug 28 in the closedposition so that gas cannot pass from gas cylinder 12 to protected room14. When piston 26 and plug 28 are in the closed position, bias chamber50 is in communication with gas inlet 44 and has a gas pressure equal togas cylinder 12.

Control chamber 52 is located between piston 26 and piston chamber 42 ofinterior cavity 36 and has a diameter D₄ equal to second diameter D₄ ofpiston chamber 42 of interior cavity 36. Belleville spring 32 is locatedin piston chamber 42 of interior cavity 36 between intermediate section40 of interior cavity 36 and piston 26. When self-regulating valve 16 isclosed, the pressure in control chamber 52, which is equal to thepressure in cylinder 12, acts on piston 26 and overcomes the springforce of Belleville spring 32 and maintains piston 26 in the closedposition.

Piston 26 has a rod section 54 housed in plug chamber 38 andintermediate section 40 of interior cavity 36 and a head section 56housed in piston chamber 42 of interior cavity 36. Rod section 54 ofpiston 26 has a diameter D₅ sized to engage intermediate section 40 ofinterior cavity 36 and includes end portion 58 having a diameter D₆smaller than diameter D₅ of rod section 54. O-ring 60 is positionedaround rod section 54 of piston 26 to ensure that gas does not passthrough intermediate section 40 of interior cavity 36. Head section 56of piston 26 has a diameter D₃ sized to engage piston chamber 42 ofinterior cavity 36 and includes end portion 62 having diameter D₄smaller than diameter D₃ of head section 56. Piston 26 is slidablewithin interior cavity 36 between a closed position and an openposition. When piston 26 is in the closed position, Belleville spring 32is fully compressed and head section 56 of piston 26 is positionedproximate intermediate section 40 of interior cavity 36. When piston 26is in the open position, head section 56 of piston 26 is proximatepiston chamber 42 of interior cavity 36. O-ring 64 is positioned aroundhead section 56 of piston 26 and maintains a seal around head section 56such that gas cannot enter piston chamber 42 from control chamber 52.

Plug 28 is housed in plug chamber 38 of interior cavity 36 and has acontrol contour end 66 and a main section 68. Plug 28 is contoured suchcontrol contour end 66 of plug 28 is sized to engage gas inlet 44 andmain section 68 of plug 28 is sized to engage plug chamber 38 ofinterior cavity 36. O-ring 70 around main section 68 of plug 28 preventsgas from entering plug chamber 38 from bias chamber 50. Plug 28 has twoinner diameters, first diameter D₆ and second diameter D₇. First innerdiameter D₆ of plug 28 is sized to engage end portion 58 of rod section54 of piston 26. Second inner diameter D₇ of plug 28 is sized to engagerod section 54 of piston 26 and hold down spring 30 encompassing rodsection 54 of piston 26. Plug 28 is movable between a closed position, apartially open position, and an open position. Plug 28 is in the closedposition when control contour end 66 of plug 28 is engaging gas inlet 44of interior cavity 36. Plug 28 is in the partially open position wheninner diameters D₆ and D₇ of plug 28 are fully engaging piston 26. Plug28 is in the fully open position when main section 68 of plug 28 abutsinterior cavity 36 where plug chamber 38 of interior cavity 36 andintermediate section 40 of interior cavity 36 join together. When plug28 is in the closed position, control contour end 66 of plug 28 sits ingas inlet 44, blocking primary passage 72 (shown in FIGS. 5 and 6)connecting gas inlet 44 and gas outlet 46. A soft seal 74 encompassescontrol contour end 66 of plug 28 and provides a secure seal between gasinlet 44 and plug chamber 38 of interior cavity 36 where plug 28 engagesgas inlet 44 to ensure that gas is not allowed to flow from gas inlet 44to gas outlet 46.

A flow passage 76 extends through interior cavity 36 from gas inlet 44to control chamber 52. Flow passage 76 passes through plug 28 and piston26 and allows gas in gas cylinder 12 to be in communication with biaschamber 50 and control chamber 52. In the closed position, plug 28 isdisengaged from piston 26, allowing gas to flow through flow passage 76in control contour end 66 of plug 28, around end portion 58 of rodsection 54 of piston 26, and into bias chamber 50. Flow passage 76 alsoallows gas from gas cylinder 12 to pass from gas inlet 44 through plug28 and piston 26 to control chamber 50. Thus, when piston 26 and plug 28are in the closed position, gas cylinder 12, bias chamber 50, andcontrol chamber 52 have equal gas pressures.

Slidable spool 34 is engageable with bleed passage 48 and controls theflow of gas from bias chamber 50 to the atmosphere. Slidable spool 34includes a passage 78 and is slidable between a closed position and anopen position. When slidable spool 34 is in the closed position, passage78 of slidable spool 34 is not aligned with bleed passage 48, preventinggas from leaving bias chamber 50 through bleed passage 48. When slidablespool 34 is in the open position, passage 78 of slidable spool 34 isaligned with bleed passage 48, allowing gas to leave from bias chamber50 through bleed passage 48. In one embodiment, slidable spool 34 is aSchraeder valve.

FIGS. 4-6 show sectional views of self-regulating valve 16 in a fullyclosed position, a partially open position, and a fully open position,respectively. FIG. 4 is a sectional view of self-regulating valve 16 inthe fully closed position mounted on cylinder 12. When self-regulatingvalve 16 is in standby for fire protection, slidable spool 34 is poweredoff and bleed passage 48 is blocked so that gas cannot leave biaschamber 50. Gas from gas cylinder 12 flows through flow passage 76 suchthat gas cylinder 12, bias chamber 50 and control chamber 52 are filledwith inert gas and have the same pressure. Due to the pressure appliedon main section 64 of plug 28 from the gas in bias chamber 50 and holddown spring 30, control contour end 66 of plug 28 engages gas inlet 44and seals primary passage 72 such that gas cannot pass through primarypassage 72 to gas outlet 46. Additionally, passage 78 of slidable spool34 is not aligned with bleed passage 48 such that gas cannot be expelledfrom bias chamber 50 to the atmosphere.

FIG. 5 is a sectional view of self-regulating valve 16 in a partiallyopen position. When there is a need to discharge gas from cylinder 12,slidable spool 34 is moved to the open position such that passage 78 ofslidable spool 34 is aligned with bleed passage 48 and gas is allowed toflow from bias chamber 50 through bleed passage 48. Slidable spool 34 isnormally electrically activated by control panel 20 (shown in FIG. 1).In case of a power failure during a fire, self-regulating valve 16 canalso be opened manually by activation device 80.

As gas flows from bias chamber 50 through bleed passage 48, thepneumatic pressure differential between gas cylinder 12 and bias chamber50 move plug 28 up almost instantly to the partially open position. Plug28 eventually stops when rod section 54 of piston 26 fully engages plug28. When plug 28 is in the partially open position, control contour end66 of plug 28 is disengaged from gas inlet 44, partially opening primarypassage 72. Gas is thus able to pass through primary passage 72 from gasinlet 44 to gas outlet 46 and into protected room 14. The cross-sectionof primary passage 72 is directly correlated to the displacement of plug28, and self-regulating valve 16 opens from a minimal to a maximal areaas a function of the displacement of plug 28.

When plug 28 is in the partially open position, primary passage 72 isonly partially open so that overpressure does not occur in protectedroom 14 due to a high initial discharge of gas. Gas continues to bedischarged from flow control valve 16 at a controlled rate with primarypassage 72 open only a certain percentage. When end portion 58 of rodsection 54 of piston 26 engages plug 28, gas can no longer pass aroundend portion 58 of rod section 54 of piston 26 into bias chamber 50.O-ring 82 around end portion 58 of rod section 48 of piston 26 seals anypassage into bias chamber 50 around piston 26 and ensures that gas doesnot enter bias chamber 50. Although gas cylinder 12 and bias chamber 50are no longer in communication, gas cylinder 12 and control chamber 52are still in communication through flow passage 76. As gas continues toflow into protected room 14, the pressures in gas cylinder 12 andcontrol chamber 52 gradually decrease and piston 26 along with plug 28begins to move to the open fully position.

FIG. 6 shows self-regulating valve 16 in a fully open position. Becausegas cylinder 12 and control chamber 52 are in communication with eachother, as gas is released into protected room 14, the pressures in gascylinder 12 and control chamber 52 decrease at the same rate. Once thepressure in control chamber 52 has decayed to a predetermined level, theforce of Belleville spring 32 begins to overcome the pressure exertedagainst head section 56 of piston 26 in control chamber 52. Piston 26and plug 28 thus begin to move together to the open position due to thepressure exerted against control contour end 66 of plug 28 by the gasleaving gas cylinder 12 through gas inlet 44. As a result, primarypassage 72 continues to open and the gas in gas cylinder 12 are releasedinto protected room 14 at a relatively constant rate to ensure that therequisite amount of gas is discharged into protected room 14 withinspecified time limits and without causing overpressure in protected room14. Self-regulating valve 16 is in the fully open position when headsection 56 of piston 26 abuts piston chamber 42 of interior cavity 36and primary passage 72 is fully open. The rate of gas release fromself-regulating valve 16 is thus controlled by the pressure decayprofile in gas cylinder 12 and by the contour of control contour end 66of plug 28.

FIG. 7 shows self-regulating valve 16 after the gas in gas cylinder 12has been discharged and self-regulating valve 16 needs to be rechargedfor subsequent use. Once most of the gas has been emitted fromself-regulating valve 16, no more pressure is exerted against plug 28,thus spring 30 starts pushing plug 28 back to the closed position. Withplug 28 in the closed position, control contour end 66 of plug 28engages gas inlet 44 such that primary passage 72 (shown in FIGS. 5 and6) is closed. Because there is no force acting on head section 56 ofpiston, the force of Belleville spring 32 maintains piston 26 in theopen position. Plug 28 is thus disengaged from piston 26, allowingcommunication between gas cylinder 12 and bias chamber 50 around endportion 58 of rod section 54 of piston 26. Gas cylinder 12 is also incommunication with control chamber 52 through flow passage 76. Slidablespool 34 is manually moved back to the closed position to ensure that asgas is passed into bias chamber 50, the gas will not leaveself-regulating valve 16 through bleed passage 48.

After slidable spool 34 is moved to the closed position, gas is passedthrough charging port 84 into gas cylinder 12, bias chamber 50, andcontrol chamber 52. As gas flows into control chamber 52 and begins toequalize throughout self-regulating valve 16, the pressure in controlchamber 52 eventually overcomes the spring force of Belleville spring 32and piston 26 moves to the closed position. When cylinder 12 is fullycharged, gas cylinder 12, bias chamber 50, and control chamber 52 haveequal pressures and piston 26, plug 28, and slidable spool 34 are in theclosed position.

FIG. 8 is a graph of rate of release of gas A from a prior art flowcontrol valve and rate of release of gas B from self-regulating valve16. As can be seen in FIG. 6, prior art flow control valves release gasinto an enclosed room at a dangerously high pressure in a very shortperiod of time. This can pose a danger to any personnel and equipment inthe enclosed room when the gas is released. By contrast, self-regulatingvalve 16 releases gas into the enclosed room at a controlled rate. Theinitial rate of release of gas gradually increases and generally levelsoff as self-regulating valve 16 opens. As the gas in self-regulatingvalve 16 is released and the level of gas remaining in self-regulatingvalve 16 decays, the gas pressures in cylinder 12, bias chamber 50, andcontrol chamber 52 and the rate of gas release gradually decrease untilthere is a nominal amount of gas left in self-regulating valve 16 and nomore gas is emitted.

The self-regulating valve of the present invention controllably releasesinert gas from a gas cylinder into an enclosed space upon detection of afire. The self-regulating valve has a piston and plug housed in theinterior cavity of the valve body. The piston is slidable between aclosed position and an open position. The plug is slidable between aclosed position, a partially open position, and a fully open position.The piston and the interior cavity of the valve body form a bias chamberat one end of the interior cavity and a control chamber at the oppositeend of the interior cavity. When the self-regulating valve is in standbymode, the gas cylinder, the bias chamber, and the control chamber areequally pressurized and both the piston and the plug are biased towardthe closed position by the pressure applied to the piston in the controlchamber and a plug spring.

When the plug is in the closed position, the plug engages a gas inletsuch that a primary flow passage connecting the gas inlet and a gasoutlet is fully closed. After a slidable spool is actuated, gas isallowed to bleed from the bias chamber to the atmosphere. As gas isreleased from the bias chamber, the pneumatic pressure differentialbetween the bias chamber and the gas cylinder causes the plug to movealmost instantaneously to the open position, stopping when it engagesthe piston. When the plug is in the partially open position, the primarypassage is partially open. This allows gas to pass from the gas cylinderthrough the primary passage and into the enclosed room at a controlledrate.

After all the gas has been bled from the bias chamber, the pressures inthe gas cylinder and the control chamber begin to equalize and decreaseas the gas is released. At a predetermined level, the spring force ofthe spring positioned in the control chamber overcomes the pressureexerted against the piston in the control chamber and allows the pistonand the plug to move to the fully open position. As the piston and theplug move to the fully open position, the primary passage increases incross-sectional area, allowing a second burst of gas to be released fromthe self-regulating valve into the protected room. The competing forcesof the springs, the contour of the plug, and the pneumatic pressures inthe gas cylinder, the bias chamber, and the control chamber control therate of movement of the plug and the rate of gas release into theenclosed room.

Although the present invention has been described with reference topreferred embodiments, workers skilled in the art will recognize thatchanges may be made in form and detail without departing from the spiritand scope of the invention.

1. A two-step, self-regulating valve for controlling gas flow from a gascylinder in high pressure systems, the valve comprising: a valve body; apiston movable within the valve body along an axis between a first and asecond position; a plug movable within the valve body along the axisbetween a valve closed position, a partially open position, and a fullyopen position; a valve actuator that allows the plug to move from thevalve closed position to the partially open position; and a pistonactuator that causes the piston to move from the first position to thesecond position when a gas pressure in the gas cylinder is less than asetpoint to allow the plug to move from the partially open position tothe fully open position.
 2. The two-step, self-regulating valve of claim1, wherein the valve body has an interior cavity, the interior cavityhaving a first end and a second end.
 3. The two-step, self-regulatingvalve of claim 2, and further comprising a bias chamber located in thefirst end of the interior cavity and a control chamber located in thesecond end of the interior cavity.
 4. The two-step, self-regulatingvalve of claim 3, and further comprising a flow passage connecting thegas cylinder, the bias chamber, and the control chamber.
 5. Thetwo-step, self-regulating valve of claim 4, and further comprising ableed passage connected to the bias chamber, wherein the gas pressure isvented to the atmosphere through the bleed passage.
 6. The two-step,self-regulating valve of claim 4, and further comprising a slidablespool engageable with the bleed passage and slidable between a closedposition and an open position.
 7. The two-step, self-regulating valve ofclaim 3, wherein the plug is urged towards the partially open positionby a decreasing pneumatic pressure in at least one of the chambers. 8.The two-step, self-regulating valve of claim 3, wherein the pistonactuator is a spring and wherein the piston is urged towards the secondposition by a decreasing pneumatic pressure in at least one of thechambers and the spring.
 9. The two-step, self-regulating valve of claim3, wherein the plug engages the piston when the plug is in the partiallyopen position, and wherein the piston moves to the second position andthe plug moves to the fully open position simultaneously as a functionof a decreasing pneumatic pressure in the control chamber.
 10. Thetwo-step, self-regulating valve of claim 1, wherein a rate of gasrelease from the self-regulating valve is based on a contour of theplug.
 11. An open loop pneumatic flow control valve for controlled gaspressure release from a gas cylinder in a protected room, the open looppneumatic flow control valve comprising: a valve body; a piston movablebetween a first position and a second position within the valve body; aplug movable between a closed position, a partially open position, and afully position within the valve body; and an activation device; whereinthe plug moves from the closed position to the partially open positionin response to activation of the activation device, and wherein the plugmoves from the partially open position to the fully open position andthe piston moves from the first position to the second position inresponse to a decreasing pressure in the gas cylinder.
 12. The open looppneumatic flow control valve of claim 11, and further comprising a biaschamber and a control chamber located within the valve body.
 13. Theopen loop pneumatic flow control valve of claim 12, and furthercomprising a flow passage connecting the gas cylinder, the bias chamber,and the control chamber.
 14. The open loop pneumatic flow control valveof claim 13, and further comprising a bleed passage for venting gaspressure from the bias chamber to the atmosphere.
 15. The open looppneumatic flow control valve of claim 14, wherein the plug is urged fromthe closed position to the partially open position by a decreasingpneumatic pressure in the bias chamber.
 16. The open loop pneumatic flowcontrol valve of claim 15, wherein the plug is urged from the partiallyopen position to the fully open position and the piston is urged fromthe first position to the second position by a decreasing pneumaticpressure in the control chamber.
 17. The open loop pneumatic flowcontrol valve of claim 11, and further comprising a primary passageconnecting the gas cylinder to the atmosphere, wherein the primarypassage opens progressively from a minimal to a maximal area as the plugmoves from the closed position to the partially open position and fromthe partially open position to the fully open position.
 18. A method forautomatically releasing gas from a gas container into a pipe in twophases, the method comprising: actuating an actuation device connectedbetween a valve body and a bleed passage; moving a plug from a closedposition to a partially open position in response to a first pneumaticpressure differential between the valve body and the pipe; and urging apiston from a first position to a second position, and urging the plugfrom the partially open position to a fully open position in response toa second pneumatic pressure differential between the valve body and thegas container.
 19. The method of claim 18, wherein urging the piston tothe second position is further in response to a spring.
 20. The methodof claim 18, wherein the actuation device is a slidable spool.
 21. Themethod of claim 18, wherein the actuation device is a Schraeder valve.